This invention relates to a method and apparatus for inspecting a figure. More particularly, it relates to a method and apparatus for inspecting a figure inscribed on a curved surface, for example, a letter or character inscribed on a mouthpiece of a glass tube fuse.
The figure drawn on a curved surface, for example, an inscription on the curved surface of the mouthpiece of the glass tube fuse, is difficult to inspect automatically, and hence is inspected visually by an operator. Thus, the characters inscribed on the outer periphery of the mouthpiece, such as rated current values or withstand voltages, or symbols, such as UL or CSA standard marks or type A marks for electrical components, are visually inspected, as the glass tube fuse is manually rotated about its axes.
Such manual inspection suffers from the problems that the inspection is in need of skill and is susceptible to fluctuations in the results. In addition, since the inscriptions are difficult to view precisely, the inspector's eyes become fatigued. Further, the inspection is a monotonous and physically hard operation. In other words, the inspection imposes increased cost in manpower inclusive of the cost of pedagogy and training.
On the other hand, the glass tube fuse is an electrical component which is used in large quantities in the field of consumer equipment and which is critical from the viewpoint of safety standards. In order to acquire recognition of the so-called ISO 9000 series, the debut of a suitable inspection device which takes the place of visual inspection has been strongly desired.